I recently purchased a 93 LT1 and the SES light came on as I was driving it home. I did the flash diagnostic and came up with a code 33 which is: Manifold Absolute Pressure (MAP) sensor circuit (signal voltage high, low vacuum)

My question is does this mean I need to replace the MAP or is it indicating another problem I should look for?

 

The code sets when the MAP reads 68kPa, with a throttle position of less than 4%. It can be caused by an open circuit on the black ground wire to the MAP sensor. Or, it can be caused by high misfire rate, a low unstable idle, or a large cam.

The connector often produces the codes. The connectors seem to "dry out" and crumble, causing intermittent contact. Check the sensor connector and see if its falling apart.

 

You could also get the code from a poor idle or engine unexpectedly dying (the MAP code just being a result-not the cause). Since you don't indicate drivability problems, you might just want to clear the code and see if it returns.

 

Here's an update. I was messing around under the hood looking at The MAP and the wiring (Injuneer mentioned this) and noticed the previous owner (or owner before him) either put a new connector on for the map or something because the wires running into the MAP have been spliced in to the main harness with electrical tape. I wiggled some of the wires and then when I tried to start the car it wouldn't start unless I held the gas down and then would die if I didn't keep my foot on the gas pedal. During this time the car was running crazy rich. So I went back and undid the clip from the MAP and put it back on, I also squeezed the electrical tape at all the splices and then it fired right back up and idled just fine. The SES light is now no longer on. So I'm thinking I need to either rewire the current mess or get a new MAP connector harness and splice it into the main harness. Any thoughts on where to get the new harness, dealership, parts store?

Here is a pic to help explain the wiring mess

 

The MAP reading is extremely critical on your 93 LT1 because it runs in speed-density. If the faulty kPa reading is 2X the actual manifold pressure, the ECM will calculate 2X the actual intake air flow, and will add 2X the required amount of fuel.

 

I just installed a few new harnesses myself.

Id reccommend these guys:

http://stores.shop.ebay.com/Auto-Wir...__W0QQ_armrsZ1

Very professional, correct pieces, and prices are great.

Keep her on the road and good luck!,
Ivan

 

Thanks guys, I'm gonna go rewire my MAP now and see how that works. If not, then I'll order a new connector and redo it.

 

Also, there is some kind of gasket in the map sensor that goes bad.Might replace that.My02

 

The link posted above does not work for me, but http://www.eficonnection.com/eficonn..._pigtails.aspx is a good place to get new pigtails. You can probably just fix what you have with some solder and heatshrink, though.